Given a self-map $h$ of a (closed?) manifold, is there a vector field $\xi$ with flow $\Phi_t$ such that $h = \Phi_1$? Given a (closed?) connected Riemannian manifold $M^n$ and a self-diffeomorphism $h: M \to M$, is it necessarily the case that there is a differential equation/smooth, tangent vector field $\xi$ on $M$ so that the flow $\Phi_t$ of $\xi$ has $h = \Phi_1$? That is, can we always extend a discrete-time dynamical system to a continuous-time one?
Thanks in advance.
EDIT: Here is a follow-up question: Follow-Up to given a self-map $h$ of a (closed?) manifold, is there a vector field $\xi$ with flow $\Phi_t$ such that $h=\Phi_1$?
 A: If $h = \Phi_1$ for some flow $\Phi$ then clearly $h$ is homotopic to the identity. So, one can obtain many counterexamples by simply constructing self-diffeomorphisms that are not homotopic to the identity, and one can detect this using reasonably simple invariants of algebraic topology.
For one example, any orientation reversing diffeomorphism of a closed, oriented manifold $n$-manifold $M$ is not homotopic to the identity, because it induces the "multiplication by $-1$" map on $H_n(M;\mathbb R) \approx \mathbb R$. (This works as well for connected oriented manifolds, but the obstruction is a bit harder to describe).
For another example, the torus $T^2 = S^1 \times S^1$ has fundamental group isomorphic to $\mathbb Z \times \mathbb Z$. For any matrix $M \in SL(2,\mathbb Z) = \text{Aut}(\mathbb Z \times \mathbb Z)$ there exists a diffeomorphism $\phi_M : T^2 \to T^2$ such that the automorphism of $\pi_1(T^2) \approx \mathbb Z \times \mathbb Z$ induced by $\phi_M$ is given by the matrix $M$. Thus $\phi_M$ is not homotopic to the identity if $M$ is not the identity matrix.
A: Not every diffeomorphism stems from a flow. See for example Section 2 (General results) of Flows and diffeomorphisms by Jaime Arango and Adriana Gómez.
Consider for example the diffeomorphism $x \mapsto -x$.
See also this question and answer for related details.
A: Per a comment by Jason DeVito, there are even self-diffeos which are isotopic to the identity, but which are not flows; see, for example, diffeomorphism which is not a translation of the integral curve for some vector field.
Also, per a suggested post in the right column while viewing this, we have the also interesting question/answers Does the set of diffeomorphisms which are induced by flows form a group?
